The present invention relates to a power supply for converting a line source alternating current (AC) to a reduced voltage direct current (DC). More particularly, the present invention relates to a phase regulated AC to DC power supply for powering a brushless DC motor.
Brushless DC motors are known to be both highly efficient and economical. Motors of this type are employed in a number of applications ranging from office equipment to industrial robotics. The home appliance market, however, has yet to take full advantage of the efficiency and cost savings inherent in brushless DC motors. For example, household refrigerators typically include AC motors to operate the compressor, condenser and evaporator, and these motors account for about 20% of the total energy consumed by an average household.
One solution to increase power efficiency in all household appliances using AC motors is to replace such motors with brushless DC motors. For example, if the AC evaporator and condenser motors in a refrigerator are replaced by DC motors the overall power efficiency increases 20%-30%. However, to operate DC motors from a standard 110 volt or 220 volt line source requires an AC to DC power supply. Conventional AC to DC power supplies include line regulated power supplies and switching power supplies. A disadvantage in using a line regulated power supply is that a bulky and expensive line frequency transformer is required. The large size of the power supply is clearly a disadvantage from the standpoint of space conservation, since the power supply cannot fit within the motor housing. While, switching power supplies are generally smaller in size, they include relatively expensive switching components.
Therefore, in response to the foregoing problems, it is an object of the present invention to provide an AC to DC power supply which eliminates the need for a bulky transformer and is small enough to fit within the housing of a brushless DC motor.
It is another object of the present invention to provide an AC to DC power supply which does not utilize the expensive switching components found in prior art power supplies.